To add to a few of your questions that have already been answered:
I have my stir crazy on a switch. I found that my turbo oven isn't
powerful enough. You may find the same problem and would like the switch
option. I must say that you will need a switch the the heating element
because otherwise your roasts are done faster than you can say "espresso".
Secondly, my copper cap is notch on both sides. I didn't drill a hole,
and in retrospect that may have been the way to go. Currently I'm using
500F silcone sealant squeezed up under the cap. I was worried at first
about fumes and other toxins from it, but so far I've gotten nothing but
good results and the sealant holds the cap fine.
Good luck and enjoy the building process.